An image forming apparatus (e.g., copier, facsimile, and printer) may include an optical scanning unit for writing a latent image on an image carrier. Such an optical scanning unit may have various configurations, as required.
One optical scanning unit may use a semiconductor laser having a laser-emitting element as a light source. Such a semiconductor laser may be a laser diode (hereinafter, LD), for example.
Such an optical scanning unit may have a LD (laser diode) unit to hold the laser diode. The LD unit may be fixed to an optical housing of the optical scanning unit.
In general, the LD unit may be fixed to the optical housing with a fastening member such as screw, for example. In such a configuration, a position of the LD unit with respect to the optical housing may not be moved (or deviated) after fastening the LD unit to the optical housing.
However, if the LD unit is attached and fixed to the optical housing with an elastic member, for example, leaf spring, the LD unit may have some clearance with the optical housing, although such clearance may be small. In such a configuration, a position of the LD unit with respect to the optical housing may be relatively moved (or deviated) because of such clearance.
Such movement of the LD unit may change a position of the LD unit with respect to the optical housing, by which a direction of light beam emitted from the LD unit may be deviated from an optimal condition. Such a directional deviation of the light beam may cause a deviation of scanning line on an image carrier, for example, photoconductive member.
In case of a monochrome machine or single-beam machine, such directional deviation of light beam may not cause a significant degradation of image quality.
However, for a full-color machine having a plurality of photoconductive members (e.g., photoconductive drums), such directional deviation of light beams may cause a degradation of image quality, for example, misaligned color images.
Further, if a plurality of LD units may be used in the image forming apparatus, such directional deviation of light beams may cause pitch misalignment between each color on image carriers, by which image quality may degrade.